1. Field of the Invention
This invention relates a thin film planar structure and a method for producing the same, and more particularly the same structure and the same method suitable for parts constituting micro machines such as a micro actuator, cats, various sensors such as a micro sensor, various probes such as a sensor for a scanning probe-microscope, etc.
2. Description of the Prior Art
One side-fixed beams having good shape-accuracy, as their component, separated from substrates are desired for micro machines, various sensors, various probes, etc. Thus, planar structures such as beams composed of various thin films are being used by employing micro machining applied from thin film-forming techniques and micro processing techniques in manufacturing semiconductors.
The above thin film-planar structures are generally produced through the steps shown in FIGS. 1-4. FIG. 1 is a plan view showing a first step of a conventional method for producing a thin film-planar structure. FIG. 2 is a cross sectional view taken on line Ixe2x80x94I of the plan view of FIG. 1. FIGS. 3 and 4 show steps after the step of FIGS. 1 and 2 with time.
First of all, as shown in FIGS. 1 and 2, after a resist is applied uniformly on a main surface 1A of a substrate 1, it is exposed and developed to form a patterned provisional layer 2. Then, as shown in FIG. 3, a thin film made of metal material or silicon material is formed, to cover the provisional layer 2, uniformly on the main surface 1A of the substrate 1. The thin film is etched to form a thin film-processed body 3 patterned into a given shape.
However, the thin film-planar-structure as shown in FIG. 4 is not often obtained, depending upon various conditions in producing the thin film-processed body 3, which results in a three-dimensional structure formed by the bending of the thin film-processed body 3 as shown in FIG. 5 or the destruction of the thin film-processed body 3 due to its too large bending as shown in FIG. 6.
The reasons for the above phenomena are that the internal stress-distribution of the thin film-processed body 3 is not uniform in the direction along its thickness. Accordingly, for making the internal stress uniform in the thickness direction, a gas pressure, a substrate temperature, an evaporation temperature or a sputtering output power etc. in forming, by a vapor deposition method, sputtering method or the like, the thin film uniformly before etching tried to be controlled appropriately. Moreover, for the object, the etching conditions tried to be also controlled variously.
The film-forming conditions in sputtering seriously influence the natures of the thin film-processed body 3. For example, if a gas pressure in sputtering is increased, its internal stress is decreased, but the density of the thin film-processed body 3 itself is degraded. As a result, the thus obtained thin film-planar structure is often degraded in mechanical strength and can not be often processed in a desired shape due to too etching in a successive etching process.
The internal stress of the thin film-processed body 3 is sensitive to such film-forming conditions. Thus, since precise controlling of the above film-forming conditions is required, it is difficult to obtain the thin film-planar structure in good reproducibility.
Moreover, the above various controlling of the etching conditions has difficulty figuring out the appropriate conditions to realize the relaxation of the internal stress and the etching the thin film at the same time,
It is an object of the present invention to provide a thin film-planar structure and a method for producing the same, capable of being produced in good reproducibility through controlling the internal stress.
This invention relates to a thin film-planar structure composed of a thin film made of an amorphous material having a supercooled liquid phase region.
This invention also relates to a method for producing a thin film planar structure comprising the steps of:
forming on a substrate a thin film made of an amorphous material having a supercooled liquid phase region,
processing the thin film into a given shape to form a thin film-processed body,
heating the thin film-processed body to a temperature within the supercooled liquid phase region,
cooling down the thin film-processed body to a room temperature from the temperature within the supercooled liquid phase region and holding it at the temperature for a given time,
removing at least a part of the substrate to produce the thin film-planar structure composed of the thin film-processed body.
This invention further relates to a method for producing a thin film-planar structure comprising the steps of:
forming on a substrate a patterned provisional layer,
forming on the substrate a thin film made of an amorphous material having a supercooled liquid phase region so as to cover the provisional layer,
processing the thin film into a given shape to form a thin film-processed body,
heating the thin film-processed body to a temperature within the supercooled liquid phase region and holding it at the temperature for a given time,
cooling down the thin film-processed body to a room temperature from the temperature within the supercooled liquid phase region, and
removing the provisional layer to produce the thin film-planar structure composed of the thin film-processed body.
To iron out the above problems, this inventors has been intensely studied to develop a new material constituting the thin film-planar structure and a method for producing it. At last, they have found a way to solve the above problems as follows:
The thin film-planer structure is formed of a thin film made of an amorphous material having a supercooled liquid phase region, and the thin film is heated to a temperature within the supercooled liquid phase region.
That is, when the thin film made of the amorphous material having the supercooled liquid phase region is heated, it exhibits glass-transition phenomenon. Just then, the once solid and high rigid thin film becomes semisolid (supercooled liquid) and becomes in viscous flow of a viscosity of 108-103 Paxc2x7S. Thus, the internal stress generated in the thin film due to sputtering is relaxed.
Consequently, when the thin film is cooled down to room temperature and the provisional layer or a part of the substrate is removed, the thin film is not bended or destroyed.
This invention has been realized through this inventors"" finding and attention of the above natures of the amorphous material having the supercooled liquid phase region and taking advantage of the natures.
Herein, the wording xe2x80x9ca supercooled liquid phase regionxe2x80x9d is a temperature region from a glass-transition temperature (Tg) to a crystallizationstarting temperature (Tx).
Moreover, the wording xe2x80x9ca thin film-planar structurexe2x80x9d is a structure composed of a thin film-processed body formed by etch-processing in plane a thin film made of an amorphous material as above-mentioned, different from a structure composed of a thin film-processed body formed by three-dimensionally processing the thin film.